INFLUENCE OF TILLAGE PRACTICES ON ANTHRACNOSE DEVELOPMENT AND DISTRIBUTION IN DRY BEAN FIELDS

Three tillage practices-chiseling rototilling, and moldboard plowing-w ere evaluated in 1993 and 1994 to determine their impact on initial di sease development, distribution, and progression over time in a field of the susceptible kidney bean cultivar Horizon. The tillage treatment s were administered in the spring in a field infested in 1992 with the bean anthracnose pathogen, Colletotrichum lindemuthianum race beta. I nitial disease incidence was highest in the chiseled plots, where more bean debris was left on the surface than in the other treatments. Sig nificantly higher final disease incidence and area under the disease p rogress curve (AUDPC) occurred in the chiseled plots than in the rotot illed and moldboard plowed plots. There was a significant correlation (r = 0.75) between the percentage of debris left on the surface and su bsequent disease incidence on pods in the field. Anthracnose incidence or severity in the field was highly correlated with disease incidence on harvested pods (r values ranged between 0.87 and 0.98). Results fr om the ordinary runs analysis showed that anthracnose occurred randoml y within the field early in the season, indicating that initial inocul um was from bean debris within the field. Later in the season, plant-t o-plant spread resulted in a more clustered distribution of diseased p lants.